A hard disk drive (HDD) is an electronic device that is able to store information digitally for use in a computing environment. The data is recorded on a magnetic layer of a planar, circular, rotating “magnetic disk,” which is commonly referred to as a “disk” or “disc.”
A typical hard disk drive includes at least one magnetic disk, and often includes multiple magnetic disks arranged as a stack of disks. A spindle motor rotates a disk while a magnetic head assembly is maintained near a surface of a disk. The head assembly includes a read head, a write head, or both. While the disk is rotated, a cushion of air is maintained between the disk surface and the head assembly, and is effective to maintain a desired distance between the disk surface and the head assembly. The head assembly is said to “fly” over a surface of the rotating disk.
The magnetic disks, heads, and appurtenant structure and devices required to allow these components to function together to store electronic data on the disks are contained in an enclosure that can include, for example, a shallow box-like metal base and a top cover to seal an opening of the base. The enclosure is sealed to prevent moisture, dust, and other types of particulate or chemical contamination from entering the enclosure, where the contamination may potentially interfere with the operation of the hard disk drive. In many such structures, a gasket is provided between the base and the top cover, and the base and top cover can be assembled to form a substantially air-tight seal. Some hard disk drive enclosures are hermetically sealed (i.e., they are “hermetic hard disk drives”). A hermetic seal is generally understood to be completely airtight. Other enclosures are substantially sealed, but not hermetically sealed, i.e., not completely air tight. These enclosures are closed and sealed with the exception of a small opening in the enclosure (usually a single hole formed in the enclosure) that allows air to flow between the interior and the exterior of the enclosure. The opening is covered by a filter, i.e., a “breather” filter or “respiratory” filter (see infra) that removes contaminants from air that passes through the opening.
For a hard disk drive to operate properly and reliably, without interruption, errors, malfunctioning, or failure, the gaseous atmosphere within its enclosure is as close as possible to free from moisture, particulate contamination, and other types of contamination such as chemical vapors, e.g., volatile organic or inorganic chemicals. Contaminants such as moisture, volatile and semi-volatile chemical vapors, and particulates, if allowed to be present at an interior of a hard disk drive enclosure, will deposit onto surfaces of magnetic disks or magnetic read or write heads. These contaminants, even in low amounts, and in a form of a vapor or a microscopic particle, if allowed to locate on a surface of magnetic disk or magnet head of a disk drive, will disrupt the proper and reliable functioning of the disk drive by causing a malfunction, error, or a catastrophic failure of the drive.
A non-moisture (i.e., organic or inorganic chemical) vapor contaminant may be derived from a component of a hard disk drive assembly, or from an environment of its manufacture. Various chemical vapor contaminants may be the result of outgassing of hydrocarbons or other chemical materials from substances or structure that becomes part of an assembled hard disk drive. Examples of such vapors include siloxanes and hydrocarbons or other organic or inorganic compounds and molecules such as those that are used in or as an oil, lubricant, solvent, adhesive, adhesive release material, plasticizer, or another material involved in the manufacture of a hard disk drive or a component of the drive. Various volatile and semi-volatile hydrocarbons and siloxanes can also be found in a cleanroom environment used for manufacturing electronic devices such as hard disk drives.
To prevent particulates (e.g., dust), moisture, and chemical contaminants from becoming present in a gaseous atmosphere of an interior of a hard disk drive or other type of electronic enclosure, filters are used to prevent entry of these contaminants into the enclosure or to remove such contaminants if present in the enclosure. One type of filter, often referred to as a breather (or respiratory) filter, can be provided at breather hole that is part of a cover or base of an enclosure. A breather filter allows air to pass between the inside and outside of the enclosure, such as due to a pressure change within the enclosure that is caused by a temperature change. The breather filter substantially prevents entry of dust, vaporized organic substances, inorganic substances, and moisture, from the outside, while allowing air to pass into the enclosure to equalize pressure. For an enclosure that is hermetically sealed, i.e., completely air tight, a breather filter is not present.
Optionally, another type of filter, a “recirculation filter,” may be included at an interior location of a sealed (hermetically, or non-hermetically) disk drive enclosure. A recirculation filter is located at the interior of the enclosure, usually at a location where air is caused to circulate internally within the enclosure during use by the disks rotating within the enclosure. One or more rotating disks that are located within the enclosure cause a flow of air within the enclosure. The recirculation filter is normally placed in a path of that airflow, typically at an internal surface or support structure of the enclosure at a location adjacent to the rotating disks. Any particulates, moisture, or other contamination (e.g., organic materials) contained in the flow of air will pass through the recirculation filter and is desirably collected by the filter.
While existing hard disk drives with various types of filters (recirculating filters and breather filters) are highly useful, are commercially successful, and provide highly effective and reliable service as hard disk drive products for consumer, commercial, and industrial applications, the computer and computer storage industries sustain an expectation for constantly improving performance. Ongoing reductions in the dimensions of electronic, magnetic, and microelectronic device features, along with constantly increasing speeds and capacities at which these devices operate, result in the need for continuous improvement of each of the assemblies and components of the devices, which includes filters of products that include a filter. In magnetic disk drives, smaller dimensions and higher operating speeds result in lower tolerances for the presence of moisture, particles, and organic contamination. Continuing need exists, therefore, to reduce the presence of contamination at the interior of hard disk drive enclosures.